Heart Health News

Typical Pregnancy Length May Vary More Than Thought

WEDNESDAY, Aug. 7 (HealthDay News) -- The natural length of
pregnancies can vary by as much as five weeks, according to a new
study.

Pregnant women typically are given a likely birth date that is
280 days after the onset of their last menstrual period. Only 4
percent of women deliver at 280 days, however, and just 70 percent
deliver within 10 days of their estimated due date.

The authors of the study said they're the first to find a way to
pinpoint the precise point at which a woman ovulates and a
fertilized embryo implants in the womb during a naturally conceived
pregnancy, and to follow the pregnancy through to delivery.

This is done by analyzing women's urine for the presence of
three hormones associated with the onset of pregnancy.

Using this information, the researchers were able to calculate
the length of 125 pregnancies, according to the study, which was
published Aug. 7 in the journal
Human Reproduction.

"We found that the average time from ovulation to birth was 268 days -- 38 weeks and two days," Dr. Anne Marie Jukic, a postdoctoral fellow in the epidemiology branch at the U.S. National Institute of Environmental Health Sciences, said in a journal news release. "However, even after we had excluded six pre-term births, we found that the length of the pregnancies varied by as much as 37 days."

The researchers were "a bit surprised" by the finding.

"We know that length of gestation varies among women, but some part of that variation has always been attributed to errors in the assignment of gestational age," Jukic said. "Our measure of length of gestation does not include these sources of error, and yet there is still five weeks of variability. It's fascinating."

It's too early to make any clinical recommendations based on the
findings and further research is required, the study authors
said.

"I think the best that can be said is that natural variability may be greater than we have previously thought, and if that is true, clinicians may want to keep that in mind when trying to decide whether to intervene in a pregnancy," Jukic said.

More information

The U.S. Department of Health and Human Services outlines how to
have a
healthy pregnancy.

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.